Several cities could lay claim to being Britain’s Capital of Beer and Simon Jenkins finds strong contenders in Bath and Bristol, where beer and tourism go hand in hand.

Bath Ales clearly had good reason to replace the front of the brewhouse with floor-to-ceiling windows. “We wanted people to see what we’re doing,” says operations manager Mick Stawniczy.

It was an expensive decision, and part of a £7m development at the West Country brewer which has thrown new light on this ambitious business in every sense, bringing its disparate operations onto a single site and providing a literal shop window for its wares.

Bath Ales has been around for 20 years, largely concentrating its attention on its local markets of Avon and Somerset, where its distinctive emblem of a leaping hare has become a frequent sight in the bars and restaurants and a guarantor of quality.

But a recent takeover by the longer-established St Austell Brewery has provided the investment to take the business to the next level, fusing the Cornwall brewer’s generations of expertise with Bath Ales’ dynamic hipster cool.

And, just in time for the high summer season, the brewhouse has opened its new on-site bar – inevitably named The Bath Tap – and started guided tours of its state-of-the-art facility where visitors can stroll in wonder beneath the vast conditioning tanks, be mesmerised by the 10,000-an-hour bottling plant and try the produce at the bar while watching the hard-working brewers going about their business.

In opening up its process to the public, Bath Ales has added a fresh attraction to a city which draws around five million visitors a year. And in dubbing its new straw-light lager Sulis, it has name-checked the water deity who has drawn visitors here for more than 2,000 years.

The Romans named this place Aquae Sulis, but the ancient Britons had discovered its hot springs centuries before. Inscriptions found here in both Latin and the ancient Celtic script, each of them a message imploring the help of Sulis to right some wrong, illustrate the central place it held in the culture of the both the natives and the invaders. To visit the baths now is to step right back to Roman times, and get a sense of how a community grew up around the spring, becoming for centuries a place of commerce, leisure and worship.

Many of the larger artefacts have been left exactly where they were discovered during extensive excavations which began in Georgian times and continue today. The vast stone columns and plinths, the stacks of tiles which held up floors and allowed rivers of water to act as an early form of central heating, the gravestones marking the last resting place of soldiers and clerics – each is sensitively displayed, with artist’s impressions and an audio commentary giving visitors a genuine feel for how these elements of Roman life knitted together.

Then there are the spectacular baths themselves. To walk among the columns and to sit beside the still waters is to get a sense not only of Roman life but of the Georgians and Victorians for whom this became a fashionable retreat.

And still the water pours through, a million mineral-rich litres every day, filtered through the rock and rising to the surface at a hand-hot 45-degrees centigrade. Given that the Romans were doing it two millennia ago, it’s perhaps surprising that only now is this endless source of heat being harnessed to ecclesiastical use, with the new heating system at Bath Abbey using the water to warm its worshippers.

Though less famed than its neighbouring attraction, the Abbey is itself well worth a visit, not least for the spectacular memorial stones around its walls. Panels in its floor are also dedicated to the dead; each is currently being chronicled and catalogued before being temporarily removed as part of a £20m programme to renew the foundations.

From Bath it’s a short hop to Bristol – and for me the must-see attraction here was the SS Great Britain, Isambard Kingdom Brunel’s great steamship. Her resurrection as a tourist attraction is every bit as spectacular as that of the baths. Here a glass ceiling, topped with a few centimetres of water, gives the impression that you are deep beneath the waves as you wander around her vast rusting hull, now anchored in the same dry dock where she first took shape in the 1840s. Once on board you can learn about her construction and her life on the waves, visit the claustrophobic cabins and get a sense of the vast gulf between the comforts offered to those in First Class and those in steerage.

Like many cities which have rediscovered their waterfront, Bristol’s docks, once a hub of worldwide trade, have now become a place of recreation, with countless bars and restaurants.

And if you’re still searching for a reason to visit, perhaps the Bristol Craft Beer Festival in September could be the perfect excuse. It’s a shop window for the remarkable resurgence in the city’s brewing culture, and if you’re feeling homesick, Magic Rock and Northern Monk will ensure that there’s a little piece of Yorkshire here, too.